This invention relates to nonvolatile memory elements formed from resistive-switching metal oxides.
Such nonvolatile memory elements are used in systems in which persistent storage is required. For example, digital cameras use nonvolatile memory cards to store images and digital music players use nonvolatile memory to store audio data. Nonvolatile memory is also used to persistently store data in computer environments.
As device dimensions shrink, scaling issues are posing challenges for the manufacture of traditional nonvolatile memory technologies. This has led to the investigation of alternative nonvolatile memory technologies, including resistive switching nonvolatile memory.
Resistive switching nonvolatile memory is formed using memory elements that have two or more stable states with different resistances. Bistable memory has two stable states. A bistable memory element can be placed in a high resistance state or a low resistance state by application of suitable voltages or currents. Voltage pulses are typically used to switch the memory element from one resistance state to the other. Nondestructive read operations can be performed to ascertain the value of a data bit that is stored in a memory cell.
Resistive switching based on metal oxide switching elements has been demonstrated. However, such switching elements often exhibit at least one of i) insufficiently high resistances for the “high” (i.e. “off”) and/or “low” (i.e. “on”) states, ii) insufficiently low off state and/or reset currents, iii) poor switching behavior, iv) poor electrical distribution, v) low yield, vi) poor thermal stability, and/or vii) poor reliability to be of use in practical devices.
It would therefore be desirable to be able to form high quality resistive switching nonvolatile memory elements that address at least some of these areas and perhaps others.